Expanding arbor



April 30, 1957 J. I. MAY

EXPANDING ARBOR Filed Sept. 20, 1954 F/Gl FIGS

A 770 RNE VS Company, Dear-born, Mich., a corporation of Delaware Application September 20, 1954, Serial No. 457,117 3 Claims. (Cl. 33-178) This application is directed to the machining art and more particularly to a novel type of expanding arbor usable for turning or inspection operations where a high degree of precision is required.

It is an object of this invention to provide an expanding arbor which is economical to manufacture, which is capable of a very high degree of precision and which may be quickly and easily inserted and removed from the work.

It is a further object of this invention to provide an arbor which may be readily calibrated to provide a ready means for measuring inside diameters.

This application is best understood by a study of the drawings in which Figure 1 is an elevation partially in section of one portion of an expanding arbor, and

Figure 2 is an elevation partially in section of another portion of this arbor, and

Figure 3 is an elevation partially in section of both parts of the arbor assembled, and

Figure 4 is a cross section of the arbor position, and

Figure 5 is a similar view of the arbor position.

In the production of this arbor, pilot is first center drilled and then ground straight and round. This pilot 10 is then cam ground to produce three equally spaced axial lobes rising about one or two thousandths of an inch above a true circle. This degree of eccentricity is given only by way of example and obviously may be varied to suit the particular circumstances. Pilot 10 is provided with a hexagonal head 11 and is drilled as at 12 for the reception of a limiting pin. A thin wall sleeve 13 is provided with a hexagonal head 14 and is center drilled. The open end of thin wall sleeve 13 is slotted as at 15 for the reception of a pin to be inserted in hole 12. Sleeve 13 is now forced over pilot 10. The three lobes on pilot 10 distort sleeve 13 into three corresponding lobes. Care is taken to arrange pilot 10 and sleeve 13 at this time so that hole 12 is at one end of slot 15. While sleeve 13 is so distorted, the assembly of sleeve and pilot as shown in Figure 3 is ground straight and round to an outside diameter slightly under the low limit inside diameter of the holes in which the tool is to be used. After this grinding operation, the wall of sleeve 13 will be appreciably thinner over the high points of the lobes than in the intermediate valleys. Note Figure 4.

To operate the arbor, the pilot is positioned within the sleeve so that pin 16, Figure 3, is at one end of slot 15 and the lobes of pilot 10 are adjacent the thinner section of sleeve 13. The arbor assembly may now easily be inserted into a hole having the proper inside diameter. The sleeve and pilot are then rotated relative to each other by means of hexagonal heads 11 and until pin 16 has moved to the other end of slot 15 and the lobes on pilot 10 have moved under the heavier portion of sleeve 13. This rotation will cause sleeve 13 to be distorted into a three lobe shape corresponding to the three lobe shape of pilot 10. Figure 5.

When this apparatus is to be used as an inspection gauge, slot 15 may readily be calibrated as shown in Figures 2 and 3 and the degree of rotation possible between pilot 10 and sleeve 13 when in the hole to be calibrated used as a direct indication of the size of the hole.

in the collapsed in the expanded States Patent 0 The action of the arbor is more clearly illustrated in Figures 4 and 5 in which it is shown in place in work piece 17. Figure 4 illustrates the expanding arbor in place with the angular relationship of pilot 10 and sleeve 13 so chosen that pin 16 is rotated to the extreme counterclockwise position in slot 15. In this drawing, the three lobes of pilot 10 have been indicated by the numeral 18. In the finished product, it will be observed that sleeve 13 has been ground over lobes 18 to produce alternate thick and thin Wall areas in sleeve 13. It will be noted that in Figure 4 a clearance exists between sleeve 13 and the inside diameter 10 of work piece 17.

In Figure 5 the expanding arbor is shown in the expanded or tightened position. In this figure the angular relationship between pilot 10 and sleeve 13 has been altered by rotating sleeve 13 with respect to pilot 10 until pin 16 is at the clockwise limit of slot 15. In this position the three lobes 18 are located adjacent the thickened portions of sleeve 13 and efiectively tightens sleeve 13 within inside diameter 19 of work piece 17. It is to be understood that the eccentricities shown in Figures 4 and 5 have been greatly exaggerated for purposes of illustration.

I claim as my invention:

1. The process of manufacturing an arbor compris ing establishing a central axis in a rigid pilot, machining this pilot straight and round and concentric with the central axis, establishing at least three parallel, axial lobes on the pilot, providing a sleeve having an inside diameter slightly smaller than the outside of the pilot, forcing the pilot into the sleeve whereby the sleeve is distorted by the lobes, and machining the assembly true and round and concentric with the pilot axis.

2. An arbor comprising a rigid central pilot and a hollow, thin-walled one piece sleeve, said pilot being generally cylindrical in shape and being provided with at least three longitudinal generally concentric lobes, said sleeve comprising a hollow cylindrical member with an axial opening capable of receiving said rigid central pilot and having continuous and uninterrupted side walls, said sleeve being mounted on said pilot and having alternate variations in wall thickness corresponding to the lobes of the pilot, said pilot and sleeve being capable of relative angular displacement with reference to each other.

3. An arbor comprising a rigid central pilot and a hollow, thin-walled one piece sleeve, said, pilot being generally cylindrical in shape and being provided with at least three longitudinal generally concentric lobes, said sleeve comprising a hollow cylindrical member with an axial opening capable of receiving said rigid central pilot and having continuous and uninterrupted side walls, said sleeve being mounted on said pilot and having alternate variations in wall thickness corresponding to the lobes'of the pilot, said pilot and sleeve being capable of relative angular displacement with reference to each other, and being provided with means to limit said'relative angular displacement to an amount no greater than that amount sufficient to permit the sleeve to completely expand and contract.

References Cited in the file of this patent UNITED STATES PATENTS 202,768 Vannan Apr. 23, 1878 799,912 Masterson Sept. 19, 1905' 1,005,928 Bergstrom Oct. 17, 1911 1,874,517 Hartness Aug. '30, 1932 2,196,489 Bennett Apr. 9, 1940 FOREIGN PATENTS 216,190 Switzerland Nov. 17, 1941 

